The aryl and aliphatic carboxylic acids and esters have a variety of applications in industries as anti-inflammatory drugs, fine chemicals etc. The prior art describes catalyst systems for employment in processes for the preparation of esters of carboxylic acids. So far, the most preferred catalyst system has been homogeneous palladium catalysts. Generally, the various catalyst systems used for the hydrocarbonylation of olefins contains a palladium source, a phosphine ligand and a hydrogen halide promoter. Hydrocarbonylation of olefins using a catalyst system comprising PdCl.sub.2 or PdCl.sub.2 (PPh.sub.3).sub.2, excess triphenyl phosphine and HCl has been found to occur only at drastic conditions such as 300-700 atm of CO pressure.
(Bittler et al., Agnew. Chem. Internat. Edit. 7, 1968, 329). Oi et al. (J. Mot. Cat. A. Chem., 115, 1997, 289) have reported hydroesterification of styrene using cationic palladium complexes which proceeds under mild conditions (20 atm, 80.degree. C.) to give 91 to 94% product yield in four hours (TOF=11 h.sup.-1) with n: iso ratio of 60:40. Recently, Seayed et al (Ind. Eng. Chem. Res., 37, 1998, 2180) have shown enhanced reaction rates in the hydroesterification of styrene (TOF=41 l h.sup.-1) using a catalyst system comprising of Pd(OAc).sub.2, PPh.sub.3 and p-toluene sulphonic acid with an n: iso ratio of 35:64. Even though, a variety of palladium phosphine complexes have been used for olefin hydroesterification, metal complexes which contain N- containing ligands have never been attempted.
Most of these catalyst systems cause disadvantages during the course of their employment for the preparation of carboxylic acids and esters. These include the requirement of severe conditions, use of excess ligands and promoters. Also, most of the conventional catalyst systems lose their efficacy on recycling.
Thus, there is a need for an improved process for the manufacture of carboxylic acids and esters wherein the yield and selectivity are good and the catalyst system is stable even in the absence of excess ligands.
The applicants have observed that the new transition metal complex containing a semilabile anionic ligand, which is a chelating organic compound containing a N-donor and an O.sup.- group, described in their co-pending U.S. patent application Ser. No. 09/281, 929 now U.S. Pat. No. 6,069,253 is particularly suited for use as a catalyst for the preparation of saturated carboxylic acids and esters by the hydrocarbonylation of olefinically unsaturated compounds. This transition metal complex is prepared according to the process described in said co-pending application Ser. No. 09/281,929 now U.S. Pat. No. 6,069,253. The catalyst gives good yield and selectivity and the catalyst is stable even in the absence of excess ligands and can also be recycled efficiently.